Generally, included within widely used graphical user environments, such as Windows 3.1, Windows 95, Windows NT, OS/2, UNIX X Window, Macintosh System 7, and Display Postscript, etc., are fonts and these fonts are displayed through a display device, such as a monitor. In these environments, postscript fonts of Adobe or true type fonts of Microsoft or Apple are widely used.
An outline font generally is composed of: information about the code map allotted to each character, information about the glyph indicating the shape of each character by specifying the positions of the control points, and hinting and other control information required for rasterization. This information is saved in a file called a font file.
Nowadays, approximately 1 to 10 MBytes are required to make a Korean or Chinese font. Therefore, up until now, this large amount of data has been a big hindrance to the on-line transmission of the outline characters via the network environment to another computer in a remote location which does not have the font to be used.
The normal procedure in displaying the font on a user's screen is that first, the computer's rasterizer must read the font file, and then generate a bitmap pattern. Then, the data is transmitted to the display device through a bus within a computer, or through a network, in the case of a network computer (the term `network computer` is used to include all the computers with resources distributed in the network environment). However, a problem arises when the speed requirement of data transmission exceeds that which the hardware can support.
For example, when using a network computer, the font file and the rasterizer may be located in different places in the network. This perhaps is a very typical case when a TV or a simple set-top box is used as a network computer that accesses the internet. A simple solution is of course to first transmit the needed font file to the rasterizer of the network computer through the network. However, since the entire font file has to be sent before a single character can be displayed, this clearly is not an acceptable solution.
A similar problem arises when an internet user in America tries to browse a web site in Korea. If the data is written in Korean, the user in America must already have Korean font capabilities in order to display the data from the Korean web site. If the user in America does not have Korean font capabilities the entire Korean font file must first be transmitted to the user in America from the Korean web site before Korean characters can be displayed. In this case, if the size of the Korean font file is too large, a lot of time is required to transmit the data, and this again causes a big delay in displaying the Korean fonts.
Also, even when transmitting bitmap patterns through the bus within a computer, there is a situation in which a speed problem can arise. When fast browsing of a text file is required, all the glyph information of each character must first be read before the rasterization of the font begins. This causes some delay in quick displaying of the data when there is a large amount of glyph information. That is to say, a problem in the browsing speed can occur.
Until now, speed improvement methods like font cache have been used in font displaying. However, even these improvement methods cannot solve all the problems of the transmission speed when there is nothing in the cache.